In recent years, as an electric power source for driving electric vehicles etc., use of an assembled battery made of a plurality of lithium ion secondary cells that are covered by film for instance have been made. It has been known that, with such an assembled battery, in order to maximize the charging and discharging performance of the battery (or in order to avoid reduction of battery life), each of the film-covered cells need to be cooled.
FIG. 1 shows a configuration of a conventional typical battery cell (film-covered battery). Battery cell 120 includes battery element 122 arranged inside a closed space formed by packaging film 124. Battery element 122 is comprised of alternately layered positive and negative electrode plates 111 and 115 separated by separators 112 and an electrolyte filling the closed space. Electrode tabs 125a and 125b are extracted from sealed portions 123 between packaging films. Electrode tab 125a for the positive electrode is connected to each positive electrode plate 111 via collector 113. Electrode tab 125b for the negative electrode is connected to each negative electrode plate 115 via collector 116.
In some cases, with thus configured battery cell 120, the electrode tabs may be heated to high temperatures (for example, 60 to 90 deg. C.) during usage of the battery. For this reason, there has been a risk that electrolyte will leaks out from sealed portions 123 between the films. Japanese Patent Application Laid-open 2004-103258 proposed an assembled battery configuration shown in FIG. 2 to solve this problem.
In assembled battery 150, pressure contact members 160 having elasticity are disposed between sealed portions 123 of individual battery cells 120 arranged in layers so that sealed portions 123 can be pressed by pressure contact members 160. Accordingly, even if electrode tabs 125 become high, It will be difficult for electrolyte to leak from the sealed portions. Further, pressure contact member 160 is formed with hollow 161 therein, and a cooling agent is circulated inside this hollow so as to be able cool sealed portions 123.
In this way, the countermeasure against heat in order to make the assembled battery function is a significant topic.
On the other hand, when the assembled battery is mounted on an electric vehicle, it is also very important to take preventive measures against vibration in addition to measures against heat. In particular, since the electrode tab is made of a thin metal plate, it is prone to fatigue failure if periodic vibration occurs.
Since pressure contact member 160 shown in FIG. 2 also has elasticity in addition to a cooling function, since pressure contact member 160 also has elasticity, this serves as an anti-vibration function.
Other than the above, as a countermeasure against vibration there are cases in which a module formed of a plurality of connected film-covered batteries is accommodated in a module case with anti-vibration rubber.